Elevated liver enzyme activity in construction workers: prevalence and impact on early retirement and all-cause mortality

Background: Gamma-glutamyl transferase (GGT), alanine transaminase (ALT), and aspartate transaminase (AST) are widely used as markers of hepatobiliary disorders in occupational health surveillance. Little is known, however, about the prevalence and occupational and non-occupational determinants of elevated levels of these enzymes in specific occupational groups or about the prognostic value of elevated levels with respect to long-term outcomes such as all-cause mortality and vocational disability. Methods: A cohort study was conducted among 8,043 male construction workers aged 25-64 years who had undergone occupational health examinations in 6 centers in southern Germany from 1986 to 1968 and had been followed until 1994. The prevalence of elevated levels of GGT, ALT, and AST, depending on the sociodemographic and medical characteristics determined at the baseline examination and the risk of vocational disability and all-cause mortality in relation to elevated liver enzyme activity at baseline were assessed. Covariates considered in multivariate analysis included age, nationality, occupation, body mass index (BMI), smoking, and alcohol consumption. Results: The baseline prevalence of elevated activity levels of GGT (>28 U/l at 25 degrees C), ALT (>22 U/l), and AST (>18 U/l) was 32%, 22%, and 12%, respectively. Factors most strongly related to elevated serum activity levels for all three enzymes were self-reported alcohol consumption, diabetes, and hypertension. BMI was strongly associated with elevations in GGT and ALT but not in AST. Elevated levels of AST and GGT were strongly related to early retirement and all-cause mortality. Men with AST levels exceeding 18 U/l had a 2-fold risk of early retirement and a 3 times higher risk of all-cause mortality as compared with men with lower AST levels. No significant association was observed between ALT and either of the long-term outcomes. Conclusions: Our findings suggest that screening for elevated GCT and AST levels, which are a common finding among construction workers, may be a powerful tool for the identification of individuals at increased risk of early retirement and preterm mortality and may be helpful in targeting of prevention efforts.